Enhanced supersymmetric corrections to top-quark production at the Fermilab Tevatron

We calculate the one-loop supersymmetric electroweaklike and QCD-like corrections to the top-quark pair-production cross section at the Fermilab Tevatron, including the important effects of nondegenerate top squarks and left-right top squark mixing. The largest electroweaklike effects yield a negative shift in the cross section and are enhanced right below the threshold for top-quark decay into a top squark and Higgsinolike neutralino, and can be as large as -35%. The largest QCD-like effects are positive and are enhanced for light top squark masses, and can be as large as 20%. Such shifts greatly exceed the present theoretical uncertainty in the standard model prediction, and, therefore, may be experimentally observable. We also explore the one-loop shifts in scenarios containing light top squarks and Higgsinolike neutralinos that have been recently proposed to explain various apparent experimental anomalies.